A restaurant server knows that the probability that a customer will order coffee is .30, the probability that a customer will order a diet soda is .40, and the probability that a customer will request a glass of water is .70. Explain what is wrong with his reasoning in each of the following.
a. Using Rule 2, he concludes that the probability that a customer will order either coffee or request a glass of water is .30 + .70 = 1.0.
b. Using Rule 3, he concludes that the probability that a customer will order coffee and a diet soda is (.30)(.40) = .12.